class Example{
    // 同一个文件中可操作private域名
    static void main(String[] args){
        Student st = new Student();
        st.StudentId = 1;

        st.Marks = 10;
        st.DisplayMarks();
    }
}

interface Marks{
    void DisplayMarks();
}

class Student implements Marks {
    int StudentId;
    int Marks;

    public Student(){
        super();
    }

    void DisplayMarks(){
        println(Marks);
    }
}